In the production of a usable synthesis gas by the combustion of a carbonaceous fuel, the process is operated most effectively in a gasifier or reactor under high temperature and high pressure conditions. For example, for the efficient production of a synthesis gas from a particulated coal or coke, a preferred operating temperature range of about 2400.degree. to 2600.degree. F. is maintained, at a pressure of between about 5 to 250 atmospheres.
The harsh operating conditions prevalent in such a process, and in particular the wide temperature variations experienced, imposes a severe strain on many segments of the gasifier. This type of reactor unit is normally furnished with thermal insulation as well as with a system to cool interior parts. Usually such parts as the dip tube that contacts hot effluent gases, require adequate cooling if the usable life of this member is to be preserved.
The invention is addressed to an improvement in the structure of a gasifier, and particularly in the gasifier's quench ring and cooling water distribution system. The latter, by its inherent function, is exposed to maximum temperature conditions and destructive gases. Damage often results by virtue of hot synthesis gas, which comes in direct contact with the quench ring as the hot effluent passes from the reactor's combustion chamber, into a cooling or quenching zone.
In one embodiment of a reactor structure, the combustion chamber within the reactor shell is lined with a refractory material to avoid thermal damage to the metallic shell. This refractory material can take the form of individual bricks or it can be in the configuration of a unitary member shaped of a castable refractory material. In either instance, the refractory blocks are combined and contoured to define the gasifier's constricted throat.
The refractory throat section communicated with the combustion chamber, is as a practical matter, supported in a way that throat segments can be removed if required for repair or replacement. One form of support resides in placing the quench ring in such position that it will support the throat from the underside. Thus, the quench ring, which is supportably fastened to the shell wall, will locate the throat.
However, during an operational shut down, it is probable that in the course of cooling, metallic segments of the gasifier such as the quench ring and its auxiliary parts will cool rapidly. This will allow quick access to the reactor interior for performing necessary repair or maintenance work.
When, however, the reactor's quench ring requires removal from the gasifier for repair or replacement, it is necessary to first detach the refractory blocks which make up the constricted throat. These non-metallic members require a considerably longer time period to cool than does the metallic quench ring.
Ordinarily several days might elapse before one can obtain safe access to the reactor interior to permit removal of the quench ring. Furthermore, removal of the throat refractory necessitates the expense of its subsequent replacement. This follows, since used fire brick, once disturbed, cannot be correctly reassembled.
In the instance of the gasifier metallic dip tube, this member experiences the most severe operating conditions. Even though the dip tube inner or guide surface is wetted by a coolant stream, the dip tube remains subject to thermal damage after a period of time. This results not only from the contact with the hot flowing gas along the dip tube surface, but also due to thermal stresses which develop in the metal.